Axial Elongation of Caudalized Human Pluripotent Stem Cell Organoids Mimics Neural Tube Development [RNA-Seq]

During mammalian embryogenesis, axial elongation of the neural tube is critical for establishing the anterior-posterior body axis, but is difficult to interrogate directly because it occurs post-implantation. Here we report an organoid model of neural tube extension using human pluripotent stem cell (hPSC) aggregates that recapitulates the morphologic and temporal gene expression patterns of neural tube development. Axially extending organoids consisted of longitudinally elongated epithelial compartments and contained TBXT(+)SOX2(+) neuromesodermal progenitors, PAX6(+) Nestin(+) neural progenitor populations, and MEOX1(+) paraxial mesoderm populations. Wnt agonism stimulated axial extensions in a dose-dependent manner and elongated organoids displayed regionalized rostral-caudal HOX gene expression, with hindbrain (HOXB1) expression distinct from brachial (HOXC6) and thoracic (HOXB9) expression. CRISPR interference-mediated silencing of BMP inhibitors induced elongation phenotypes that mimicked murine knockout models, and knock-down of the downstream Wnt target, TBXT, increased neuroepithelial compartmentalization and resulted in multiple extensions. These results indicate the potent morphogenic capacity of hPSC organoids to undergo axial elongation in a manner that can be used to dissect the cellular organization and patterning decisions that dictate early human nervous system development.